Clinical Toxicology (2008) 46, 218–221 Copyright © Informa Healthcare USA, Inc. ISSN: 1556-3650 print / 1556-9519 online DOI: 10.1080/15563650701378704 LCLT ARTICLE Comparison of SPECT findings and neuropsychological sequelae in carbon monoxide and organophosphate poisoning Carbon monoxide and organophosphate poisoning GURAYTEN OZYURT, FATMA NUR KAYA, FERDA KAHVECI, and ERAY ALPER Uludag University, Bursa, Turkey Abnormal regional cerebral blood flow in patients with acute carbon monoxide (CO) and organophosphate (OP) poisoning was examined using 99m Tc-hexamethylpropylene amine oxime (HMPAO) brain single photon emission computed tomography (SPECT) in fourteen patients. We evaluated the predictive significance of acute phase brain SPECT findings for long-term neuropsychological sequelae. Changes were found in the frontal, temporal, parietal lobes within the first week after both types of poisoning. The distribution of the hypoperfused cerebral areas as demonstrated by 99m Tc-HMPAO imaging was similar in the two groups during the acute phase. Neuropsychological sequelae developed in five patients poisoned with OP and six with CO. Patients who had SPECT findings heterogeneously or in the temporal or frontal lobes displayed disorientation. Those with fronto-parietal and frontal lobe changes displayed mental confusion. Parkinsonism also was observed in patients with parieto-occipital, parietal and frontal lobe lesions. The distribution of these lesions appears to predict the long term sequelae of these poisonings, though additional studies with larger numbers of patients are needed to confirm the role of SPECT imaging in both OP and CO poisonings. Keywords Carbon monoxide poisoning; Organophosphate poisoning; SPECT; Neuropsychological sequelae Introduction Carbon monoxide (CO) and organophosphate (OP) poisoning are amongst the most common causes of morbidity and mor- tality (1,2). Following exposure to CO or OP agents, morpho- logic changes are seen in some regions of the brain within a few hours (3–5). The neurotoxicity has been documented in accidental human poisoning, epidemiological studies, and animal models, and involves neuronal degeneration and sub- sequent neurological, neurobehavioral, and neuropsychologi- cal consequences in both poisonings (2–8). `Using single photon emission computed tomography (SPECT) to measure cerebral blood flow may be useful in evaluating the acute stage. Although abnormalities may be absent on MRI or CT scans, cerebral perfusion SPECT can demonstrate regional cerebral blood flow (rCBF) reductions (9,10). However, few studies have been performed on brain perfusion in patients with CO poisoning and especially OP poisoning (4–17). To the authors’ knowledge, there is no other study comparing the early SPECT findings in the two types of poisoning, both of which may both cause neurologi- cal sequelae. The aim of this study was to compare brain SPECT findings in the acute phase after CO and OP poisoning, and to investigate the relationship between SPECT findings and their subsequent neuropsychological sequelae, Materials and methods We studied 14 consecutive patients referred to our University Hospital for OP (n = 7, 5 females, 2 males) and CO (n = 7, 4 females, 3 males) intoxication from February 1995 to December 2003. This study was approved by the Ethical Committee of Uludag University Hospital and written informed consent was obtained from each patient or their legal guardians. Subjects with a previous history of psycho- logical or neurological disorders were excluded from the study. Seven patients had suffered acute exposure to CO, caused by natural gas heaters in the bathroom or by sleeping next to furnaces. Seven patients with acute OP poisoning had taken the substances orally, five in suicide attempts and two by accidental ingestion of an organophosphate insecticide. The diagnosis of poisoning was made on the basis of circum- stantial and clinical evidence. On admission, the oxygen ther- apy was begun in all patients, carboxyhemoglobin (COHb) levels or plasma cholinesterase (ChE) activities were mea- sured, and additional toxicology screening was performed to rule out other forms of poisoning. The patients were immedi- ately transferred to the intensive care unit, where oxygen sup- port was maintained, and mechanical ventilation was added when necessary. The OP poisoned patients received atropine Received 23 November 2006; accepted 2 April 2007. Address correspondence to Gurayten Ozyurt, Uludag University, Anesthesiology and Reanimation, Bursa, Turkey. E-mail: gurayten @uludag.edu.tr